Classijical'ion of the Decapod Crustaceans. 4G5 



V. 



The following tree illustrates diagrammatically the relatioii- 

 sliij) between the groups wliieh have been diseussed : — 



Brachyura, 



Aaomura 



Carides. 



raliuiua 



VI. 



I have jjrouped the families of tlie Carides into "super- 

 families," based on^ but not quite the same as, the extremely 

 suggestive " alliances " proposed by Major Alcock for the 

 Indian deep-sea families. The shape of the mandible should 

 not be followed too implicitly as an indication of affinity in 

 this group. It shows a tendency to division into " molar " 

 and "cutting" halves throughout the order. In the higher 

 Carides this division is greatly accentuated, but in some cases 

 a secondary simplicity is reached by the loss of one of the 

 halves, and this has happened independently in Latreutes 

 and the Crangonoida (cutting-edge) and, I think, Pasiplijcida: 



